This invention relates to a polishing pad assembly that is useful for chemical-mechanical polishing (CMP) in which air bubbles or pockets of air that form between the polishing pad and a polishing platen are minimized or eliminated.
Semiconductor wafers having integrated circuits fabricated thereon must be polished to provide a very smooth and flat wafer surface which, in some cases, may vary from a given plane by as little as a fraction of a micron. Such polishing is usually accomplished in a chemical-mechanical polishing (CMP) operation that utilizes a chemically active slurry that is buffed against the wafer surface by a polishing pad.
Typical pads used in CMP polishing are shown in the following patents: Cook et al. U.S. Pat. No. 6,022,264 issued Feb. 8, 2000; Roberts et al. U.S. Pat. No. 6,022,268 issued Feb. 8, 2000; Roberts et al. U.S. Pat. No. 6,019,666 issued Feb. 1, 2000; Cook et al. U.S. Pat. No. 6,017,265 issued Jan. 25, 2000; Budinger et al. U.S. Pat. No. 5,900,164 issued May 4, 1999; Roberts U.S. Pat. No. 5,605,760 issued Feb. 25, 1997; Reinhardt et al. U.S. Pat. No. 5,578,362 issued Nov. 26, 1996; Cook et al. U.S. Pat. No. 5,489,233 issued Feb. 6, 1996 and Budinger et al. U.S. Pat. No. 4,927,432 issued May 22, 1990.
In a typical polishing operation, the polishing pad is placed on a platen of a polishing machine and secured to the platen by a pressure sensitive adhesive (PSA) on the backside of the polishing pad. As the polishing pad is placed on the platen, bubbles of air tend to get trapped between the adhesive and the platen. This is a particular problem with large diameter pads, such as a typical 91 cm diameter pad, in which it is virtually impossible to eliminate trapped air. Any trapped air will distend the relatively thin pad material, thereby causing raised areas or bulges in the polishing surface of the polishing pad. Forcing the air bubbles out from under the pad with a roller is not effective. Instead, the pad in the area of the bulges must be manually pierced with a hand tool in order to let the trapped air escape, and then the pad material can be pressed against the platen to obtain the flattest possible polishing surface. This is a time-consuming process, and some small bulges often go undetected and remain in the polishing surface. Any bulges in the polishing surface will generate non-uniformities on the polished surface of the workpiece (i.e., a semiconductor wafer), thereby causing defects in the polished surface. Consequently, there is a need for a polishing pad or a polishing pad assembly that eliminates the entrapment of air between it and the polishing platen.
A polishing pad assembly is provided that is useful for the chemical mechanical polishing of glass and electrical devices, such as, semiconductor wafers that comprises a polish pad and a semi-rigid base material firmly adhered to the polishing pad for positioning on a polishing platen of a polishing machine; wherein the semi-rigid base material has a modulus of rigidity of 0.01-50 GPa (GigaPascals) determined according to ASTM D 790, a thickness of 0.25-15.0 mm, and a grooved surface having a pitch of 5-100 mm and the grooves have a width of 0.025-2.5 mm and a depth of 0.1-2.5 mm.